WO2006030677A1 - Fluoromethane production process and product - Google Patents

Fluoromethane production process and product Download PDF

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Publication number
WO2006030677A1
WO2006030677A1 PCT/JP2005/016474 JP2005016474W WO2006030677A1 WO 2006030677 A1 WO2006030677 A1 WO 2006030677A1 JP 2005016474 W JP2005016474 W JP 2005016474W WO 2006030677 A1 WO2006030677 A1 WO 2006030677A1
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fluoromethane
process according
production process
catalyst
zeolite
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PCT/JP2005/016474
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French (fr)
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Hiromoto Ohno
Tatsuharu Arai
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Showa Denko K.K.
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Publication of WO2006030677A1 publication Critical patent/WO2006030677A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/22—Halogenating
    • B01J37/26—Fluorinating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/24—Chromium, molybdenum or tungsten
    • B01J23/26—Chromium
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C17/00—Preparation of halogenated hydrocarbons
    • C07C17/093—Preparation of halogenated hydrocarbons by replacement by halogens
    • C07C17/20—Preparation of halogenated hydrocarbons by replacement by halogens of halogen atoms by other halogen atoms
    • C07C17/202—Preparation of halogenated hydrocarbons by replacement by halogens of halogen atoms by other halogen atoms two or more compounds being involved in the reaction
    • C07C17/206—Preparation of halogenated hydrocarbons by replacement by halogens of halogen atoms by other halogen atoms two or more compounds being involved in the reaction the other compound being HX

Definitions

  • the present invention relates to a process for the production of fluoromethane (CH 3 F, hereinafter also referred to as HFC-41) .
  • Hydrofluorocarbons are characterized by having an ozone depleting potential of zero and, in particular, HFC-41, difluoromethane (CH 2 F 2 ) and trifluoromethane (CHF 3 ) are useful semiconductor etching gases.
  • HFCs used as semiconductor etching gases must be of high purity and, more specifically, their acid component (hydrogen chloride, hydrogen fluoride, etc.) content is preferably no greater than 1.0 ppm by mass, while their moisture content is preferably no greater than 10 ppm by mass and more preferably no greater than 5 ppm by mass.
  • Japanese Examined Patent Publication (Kokoku) No. 4- 7330 discloses a process for the production of HFC-41 wherein methyl alcohol and hydrogen fluoride (HF) are subjected to a gas-phase reaction at a temperature of 100-500 0 C using a fluorination catalyst (chromic fluoride) .
  • a fluorination catalyst chromic fluoride
  • Japanese Unexamined Patent Publication (Kokai) No. 60-13726 discloses a process for the production of HFC-41 in which methyl chloride (CH 3 Cl) and HF are subjected to a gas-phase reaction at a reaction temperature of 100-400 0 C using a fluorination catalyst (chromic fluoride) .
  • a fluorination catalyst chromic fluoride
  • this process has become associated with a need for an improved catalytic activity and a problem of difficult separation because an azeotropic mixture is formed having a boiling point close to that of HFC-41 (boiling point at atmospheric pressure: -78.5 0 C) and hydrogen chloride (boiling point at atmospheric pressure: -84.9 0 C) .
  • HFC-41 containing substantially no hydrogen chloride (HCl) (HCl concentration: ⁇ 20 ppm by mass) can be obtained by reacting methyl chloride and hydrogen fluoride in a gas phase in the presence of a fluorination catalyst, and feeding the mixture comprising fluoromethane and hydrogen chloride to a distillation column for separation and purification of the fluoromethane and hydrogen chloride as the overhead fraction, and the present invention was thereby completed .
  • the present invention relates to an HFC-41 production process according to the following [1] to
  • step (2) a step of reacting the methyl chloride obtained in step (1) with hydrogen fluoride in a gas phase in the presence of a fluorination catalyst to obtain, predominantly, fluoromethane,
  • step (3) a step of feeding the fluoromethane-containing mixed gas obtained in step (2) to a distillation column, and separating the overhead fraction comprising, predominantly, fluoromethane and hydrogen chloride from the bottom fraction comprising predominantly methyl chloride and hydrogen fluoride, and
  • step (3) (4) a step of separating and purifying the fluoromethane from the overhead fraction obtained in step (3) .
  • a fluoromethane production process according to [1] above which further comprises a step of circulating the bottom fraction obtained in step (3) to step (2) .
  • [3] A fluoromethane production process according to [1] or [2] above, wherein the zeolite used in step (1) is Molecular Sieve 3A and/or Molecular Sieve 4A.
  • fluorination catalyst used in step (2) is a supported catalyst or bulk catalyst composed mainly of trivalent chromium oxide and containing at least one element selected from the group consisting of In, Zn, Ni, Co, Mg and Al.
  • step (2) A fluoromethane production process according to [1] or [4] above, wherein the fluorination catalyst used in step (2) is a supported catalyst supported on active alumina, wherein the active alumina has a center pore - A -
  • size of 50-400 A consisting of at least 70% pores with a distribution of ⁇ 50% of the center size and having a pore volume in the range of 0.5-1.6 ml/g, and has a purity of 99.9 mass% or greater and a sodium content of no greater than 100 ppm.
  • step (4) A fluoromethane production process according to [1] above, wherein the separation and purification step in step (4) further comprises a step of contacting the fluoromethane with water and/or an alkali-containing treatment agent to remove the acid component containing hydrogen chloride.
  • a fluoromethane production process which further comprises a step of contacting the fluoromethane with zeolite after the step of removing the acid component in the fluoromethane.
  • [10] A fluoromethane production process according to [9] above, wherein the zeolite is Molecular Sieve 3A and/or Molecular Sieve 4A.
  • [H] A fluoromethane product containing fluoromethane which is obtained by the process according to any one of [1] to [10] above and has a hydrogen chloride concentration of no greater than 1.0 ppm by mass.
  • [12] A fluoromethane product containing fluoromethane which is obtained by the process according to any one of [1] to [10] above and has a moisture concentration of no greater than 10 ppm by mass.
  • methyl chloride and hydrogen fluoride are reacted in a gas phase in the presence of a fluorination catalyst to allow efficient separation of HCl from the resulting mixture of HFC-41 and HCl, to obtain high purity HFC-41.
  • the process for production of HFC-41 according to the invention is characterized by using methyl chloride and hydrogen fluoride as the starting materials and reacting these in a gas phase in the presence of a supported, or bulk, fluorination catalyst composed mainly of trivalent chromium oxide, feeding the mixture containing HFC-41 and HCl to a distillation column and distilling and purifying the HFC-41 and HCl from the top ' of the distillation column to obtain high purity HFC-41.
  • the methyl chloride starting material is preferably contacted with zeolite in a liquid phase at a stage before supply to the reaction zone to reduce the moisture content as much as possible.
  • the zeolite is preferably Molecular Sieve 3A and/or Molecular Sieve 4A.
  • the methyl chloride and hydrogen fluoride are mixed at the reactor inlet port and introduced into the reactor.
  • the molar ratio of the hydrogen fluoride to the methyl chloride (HF/CH 3 C1) is preferably 5-30 and more preferably 8-20. If the molar ratio is less than 5, a greater proportion of impurities will be produced, and the selectivity will be poor. It is preferably not greater than 30, because the yield will be reduced and circulation of the unreacted starting materials will be increased, thus necessitating a larger apparatus.
  • the reactor is preferably a multitube type from the standpoint of preventing drift.
  • the fluorination catalyst packed in the reactor is preferably a bulk catalyst or supported catalyst composed mainly of trivalent chromium oxide.
  • a bulk catalyst is preferably composed mainly of trivalent chromium oxide and contains at least one element selected from the group consisting of In, Zn, Ni, Co, Mg and Al.
  • a supported catalyst preferably has active alumina as the catalyst support, produced having a center pore size of 50-400 A, consisting of at least 70% pores with a distribution of ⁇ 50% of the center size and having a pore volume in the range of 0.5-1.6 ml/g, and having a purity of 99.9 mass% or greater and a sodium content of no greater than 100 ppm, and supported on the active alumina is preferably trivalent chromium oxide or a material composed mainly of trivalent chromium oxide and containing at least one element selected from the group consisting of In, Zn, Ni, Co and Mg, preferably with a supporting percentage of no greater than 30 mass%.
  • fluorination catalyst is preferably subjected to fluorination treatment (catalyst activation) by hydrogen fluoride or the like.
  • the reaction temperature range is preferably 150- 350 0 C and more preferably 200-300 0 C. At below 150 0 C the reaction yield tends to be reduced, and at above 350 0 C impurities tends to increase.
  • the reaction pressure range is preferably 0.05-1.0 MPa and more preferably 0.1- 0.7 MPa. At less than 0.05 MPa the operation becomes complex, and at greater than 1.0 MPa the apparatus must be built with a more pressure-resistant structure, thus increasing costs.
  • the product (exit port) gas from the reaction in the reactor may be, for example, cooled and introduced into a distillation column by a pump, or introduced into a distillation column using a compressor.
  • the operating pressure of the distillation column is preferably in the range of 0.1-5 MPa and more preferably 0.3-3 MPa, from the standpoint of economy and operability.
  • the product gas introduced into the distillation column is separated at the top into mainly HCl and HFC-41, while at the bottom it separates into mainly the unreacted components hydrogen fluoride and methyl chloride, at least a portion of which is circulated back to the reaction step for reutilization.
  • the HFC-41 separated at the top of the distillation column contains HCl, and therefore it is contacted with water and/or an alkali-containing treatment agent to remove the HCl-containing acid component.
  • An alkali- containing treatment agent may be an aqueous alkali solution, or an alkali-containing solid material (for example, soda lime or the like) .
  • the preferred treatment agents are water and aqueous alkali solutions.
  • the preferred aqueous alkali solutions are sodium hydroxide and potassium hydroxide, with the aqueous alkali solution concentration being in the range of 0.01-20% and especially in the range of 0.1-10%.
  • the contact time is not particularly restricted but the contact temperature is preferably in a lower temperature range because of the rather high solubility of HFC-41 in water, and specifically the range is preferably 5-4O 0 C.
  • the HCl concentration of the HFC-41 subjected to acid component removal treatment is 1.0 ppm by mass or lower (measurement by ion chromatography) .
  • Example 1 Catalyst Preparation
  • Example 1 A solution of 452 g of Cr (NO 3 ) 3 - 9H 2 O and 42 g of
  • the catalyst precursor was packed into an inconel reactor, and then subjected to fluorination treatment (catalyst activation) at 350 0 C at ordinary pressure, under a nitrogen-diluted hydrogen fluoride stream and then under a 100% hydrogen fluoride stream, to prepare a catalyst.
  • fluorination treatment catalyst activation
  • Catalyst Preparation Example 2 As a catalyst carrier there was used active alumina (NST-7, by Nikki Universal Co., Ltd.) produced having a center pore size of 50-400 A, consisting of at least 70% pores with a distribution of ⁇ 50% of the center size and having a pore volume in the range of 0.5-1.6 ml/g, and having a purity of 99.9 mass% or greater and a sodium content of no greater than 100 ppm. '
  • the catalyst was then packed into an inconel reactor and subjected to fluorination treatment (catalyst activation) at 330 0 C at ordinary pressure, under a nitrogen-diluted hydrogen fluoride stream and then under a 100% hydrogen fluoride stream, to prepare a catalyst.
  • fluorination treatment catalyst activation
  • Catalyst Preparation Example 3 A catalyst was obtained in the same manner as
  • Catalyst Preparation Example 2 except that 16.57 g of zinc chloride (ZnCl 2 ) was added as a second component to the Catalyst Preparation Example 2 of Example 2.
  • Example 4 Commercially available methyl chloride (99.9 vol% purity, moisture content: 48 ppm by mass) was contacted with zeolite (Molecular Sieve 3A (Union Showa Co., Ltd., mean pore size: 3 A)) in a liquid phase before being supplied to the reaction system, and the moisture in the methyl chloride was analyzed with a moisture meter (Carl Fisher) to be 6 ppm by mass.
  • zeolite Molecular Sieve 3A (Union Showa Co., Ltd., mean pore size: 3 A)
  • moisture in the methyl chloride starting material is undesirable because it adversely affects the reaction, reducing the conversion rate and selectivity.
  • the reactor outlet gas was recovered in a vessel equipped with a cooler, and the recovered mixture was subjected to distillation.
  • the recovered mixture was first introduced into a distillation column.
  • the distillation column was provided with a condenser and had 20 theoretical plates (36 actual plates) ; the low- boiling-point components HCl and CH 3 F separated at the top of the column while the high-boiling-point components CH 3 CI and HF separated at the bottom of the column.
  • the HCl and CH 3 F separated from the top were contacted with a 2% aqueous potassium hydroxide solution at a temperature of about 5°C, and then the HCl concentration of the HFC- 41 was analyzed by ion chromatography, yielding a HCl concentration of 0.5 ppm by mass.
  • the HFC-41 After being contacted with the aforementioned aqueous alkali solution, the HFC-41 was contacted with zeolite (Molecular Sieve 3A (Union Showa Co., Ltd.)) and the moisture content of the HFC-41 was analyzed with a moisture meter (Carl Fisher) for a moisture concentration of 4 ppm by mass, demonstrating that high purity HFC-41 had been obtained.
  • zeolite Molecular Sieve 3A (Union Showa Co., Ltd.)
  • the present invention allows efficient separation of HCl from mixtures containing HFC-41 and HCl to obtain high purity HFC-41, and is therefore of high industrial utility.

Abstract

Methyl chloride and hydrogen fluoride are reacted in a gas phase in the presence of a fluorination catalyst and the resulting mixture, containing fluoromethane and hydrogen chloride, is fed to a distillation column for separation and purification of the fluoromethane and hydrogen chloride as the overhead fraction. It is thus possible to efficiently produce high purity HFC-41 which is suitable for use as a semiconductor etching gas.

Description

DESCRIPTION
FLUOROMETHANE PRODUCTION PROCESS AND PRODUCT
Cross-Reference to Related Application
This application is an application filed under 35 U. S.C. §111 (a) claiming benefit of priority pursuant to 35 U.S.C. §119(e) (l) of the filing date of the Provisional Application 60/612,538 filed September 24, 2004, pursuant to 35 U.S.C. §111 (b) . Technical Field
The present invention relates to a process for the production of fluoromethane (CH3F, hereinafter also referred to as HFC-41) . Background Art
Hydrofluorocarbons (HFC) are characterized by having an ozone depleting potential of zero and, in particular, HFC-41, difluoromethane (CH2F2) and trifluoromethane (CHF3) are useful semiconductor etching gases. HFCs used as semiconductor etching gases must be of high purity and, more specifically, their acid component (hydrogen chloride, hydrogen fluoride, etc.) content is preferably no greater than 1.0 ppm by mass, while their moisture content is preferably no greater than 10 ppm by mass and more preferably no greater than 5 ppm by mass.
Many methods have therefore been proposed for producing high purity HFCs, but these were molecules with two or more carbon atoms whereas fluorination of chloroform or fluorination of dichloromethane deals with single-carbon methane, and almost no production processes for HFC-41 have been proposed. The main reason is that, when fluorinating halogenated hydrocarbons, a larger number of hydrogen atoms in the molecule lowers the fluorination reactivity, and tends to promote decomposition and by-products.
Japanese Examined Patent Publication (Kokoku) No. 4- 7330 discloses a process for the production of HFC-41 wherein methyl alcohol and hydrogen fluoride (HF) are subjected to a gas-phase reaction at a temperature of 100-5000C using a fluorination catalyst (chromic fluoride) . However, this process introduces the problem of deterioration of the fluorination catalyst and corrosion of the reactor as a result of water as a by¬ product.
Also, Japanese Unexamined Patent Publication (Kokai) No. 60-13726 discloses a process for the production of HFC-41 in which methyl chloride (CH3Cl) and HF are subjected to a gas-phase reaction at a reaction temperature of 100-4000C using a fluorination catalyst (chromic fluoride) . However, due to the equilibrium reaction shown below as chemical equation (1), this process has become associated with a need for an improved catalytic activity and a problem of difficult separation because an azeotropic mixture is formed having a boiling point close to that of HFC-41 (boiling point at atmospheric pressure: -78.50C) and hydrogen chloride (boiling point at atmospheric pressure: -84.90C) . CH3Cl + HF ^ CH3F + HCl (1) Disclosure of Invention
It is an object of the present invention to provide a process for the efficient production of high purity HFC-41 which can be used as a semiconductor etching gas, as well as a product thereof.
As a result of much diligent research directed toward solving the problems described above, the present inventors found that HFC-41 containing substantially no hydrogen chloride (HCl) (HCl concentration: <20 ppm by mass) can be obtained by reacting methyl chloride and hydrogen fluoride in a gas phase in the presence of a fluorination catalyst, and feeding the mixture comprising fluoromethane and hydrogen chloride to a distillation column for separation and purification of the fluoromethane and hydrogen chloride as the overhead fraction, and the present invention was thereby completed .
The present invention relates to an HFC-41 production process according to the following [1] to
[H] . [1] A process for producing fluoromethane comprising the following four steps:
(1) a step of contacting methyl chloride with zeolite in a liquid phase,
(2) a step of reacting the methyl chloride obtained in step (1) with hydrogen fluoride in a gas phase in the presence of a fluorination catalyst to obtain, predominantly, fluoromethane,
(3) a step of feeding the fluoromethane-containing mixed gas obtained in step (2) to a distillation column, and separating the overhead fraction comprising, predominantly, fluoromethane and hydrogen chloride from the bottom fraction comprising predominantly methyl chloride and hydrogen fluoride, and
(4) a step of separating and purifying the fluoromethane from the overhead fraction obtained in step (3) .
[2] A fluoromethane production process according to [1] above, which further comprises a step of circulating the bottom fraction obtained in step (3) to step (2) . [3] A fluoromethane production process according to [1] or [2] above, wherein the zeolite used in step (1) is Molecular Sieve 3A and/or Molecular Sieve 4A.
[4] A fluoromethane production process according to [1] above, wherein the fluorination catalyst used in step (2) is a supported catalyst or bulk catalyst composed mainly of trivalent chromium oxide and containing at least one element selected from the group consisting of In, Zn, Ni, Co, Mg and Al.
[5] A fluoromethane production process according to [1] or [4] above, wherein the fluorination catalyst used in step (2) is a supported catalyst supported on active alumina, wherein the active alumina has a center pore - A -
size of 50-400 A, consisting of at least 70% pores with a distribution of ±50% of the center size and having a pore volume in the range of 0.5-1.6 ml/g, and has a purity of 99.9 mass% or greater and a sodium content of no greater than 100 ppm.
[6] A fluoromethane production process according to [1], [4] or [5] above, wherein the reaction temperature in step (2) is 150-3500C.
[7] A fluoromethane production process according to [1] above, wherein the distillation in step (3) is carried out in a pressure range of 0.1-5 MPa.
[8] A fluoromethane production process according to [1] above, wherein the separation and purification step in step (4) further comprises a step of contacting the fluoromethane with water and/or an alkali-containing treatment agent to remove the acid component containing hydrogen chloride.
[9] A fluoromethane production process according to [8] above, which further comprises a step of contacting the fluoromethane with zeolite after the step of removing the acid component in the fluoromethane.
[10] A fluoromethane production process according to [9] above, wherein the zeolite is Molecular Sieve 3A and/or Molecular Sieve 4A. [H] A fluoromethane product containing fluoromethane which is obtained by the process according to any one of [1] to [10] above and has a hydrogen chloride concentration of no greater than 1.0 ppm by mass. [12] A fluoromethane product containing fluoromethane which is obtained by the process according to any one of [1] to [10] above and has a moisture concentration of no greater than 10 ppm by mass.
According to the invention, methyl chloride and hydrogen fluoride are reacted in a gas phase in the presence of a fluorination catalyst to allow efficient separation of HCl from the resulting mixture of HFC-41 and HCl, to obtain high purity HFC-41.
Best Mode for Carrying Out the Invention The process for production of HFC-41 according to the invention is characterized by using methyl chloride and hydrogen fluoride as the starting materials and reacting these in a gas phase in the presence of a supported, or bulk, fluorination catalyst composed mainly of trivalent chromium oxide, feeding the mixture containing HFC-41 and HCl to a distillation column and distilling and purifying the HFC-41 and HCl from the top' of the distillation column to obtain high purity HFC-41. The methyl chloride starting material is preferably contacted with zeolite in a liquid phase at a stage before supply to the reaction zone to reduce the moisture content as much as possible. When a stabilizer is included, it must also be removed in order to maintain the catalyst life. Infiltration of moisture into the reaction zone can adversely promote corrosion of the apparatus materials and production of decomposition by- products. The zeolite is preferably Molecular Sieve 3A and/or Molecular Sieve 4A. The methyl chloride and hydrogen fluoride are mixed at the reactor inlet port and introduced into the reactor. The molar ratio of the hydrogen fluoride to the methyl chloride (HF/CH3C1) is preferably 5-30 and more preferably 8-20. If the molar ratio is less than 5, a greater proportion of impurities will be produced, and the selectivity will be poor. It is preferably not greater than 30, because the yield will be reduced and circulation of the unreacted starting materials will be increased, thus necessitating a larger apparatus.
The reactor is preferably a multitube type from the standpoint of preventing drift. The fluorination catalyst packed in the reactor is preferably a bulk catalyst or supported catalyst composed mainly of trivalent chromium oxide. A bulk catalyst is preferably composed mainly of trivalent chromium oxide and contains at least one element selected from the group consisting of In, Zn, Ni, Co, Mg and Al. A supported catalyst preferably has active alumina as the catalyst support, produced having a center pore size of 50-400 A, consisting of at least 70% pores with a distribution of ±50% of the center size and having a pore volume in the range of 0.5-1.6 ml/g, and having a purity of 99.9 mass% or greater and a sodium content of no greater than 100 ppm, and supported on the active alumina is preferably trivalent chromium oxide or a material composed mainly of trivalent chromium oxide and containing at least one element selected from the group consisting of In, Zn, Ni, Co and Mg, preferably with a supporting percentage of no greater than 30 mass%. Before use in the reaction, at least a portion of the fluorination catalyst is preferably subjected to fluorination treatment (catalyst activation) by hydrogen fluoride or the like.
The reaction temperature range is preferably 150- 3500C and more preferably 200-3000C. At below 1500C the reaction yield tends to be reduced, and at above 3500C impurities tends to increase. The reaction pressure range is preferably 0.05-1.0 MPa and more preferably 0.1- 0.7 MPa. At less than 0.05 MPa the operation becomes complex, and at greater than 1.0 MPa the apparatus must be built with a more pressure-resistant structure, thus increasing costs. The product (exit port) gas from the reaction in the reactor may be, for example, cooled and introduced into a distillation column by a pump, or introduced into a distillation column using a compressor. The operating pressure of the distillation column is preferably in the range of 0.1-5 MPa and more preferably 0.3-3 MPa, from the standpoint of economy and operability. The product gas introduced into the distillation column is separated at the top into mainly HCl and HFC-41, while at the bottom it separates into mainly the unreacted components hydrogen fluoride and methyl chloride, at least a portion of which is circulated back to the reaction step for reutilization.
The HFC-41 separated at the top of the distillation column contains HCl, and therefore it is contacted with water and/or an alkali-containing treatment agent to remove the HCl-containing acid component. An alkali- containing treatment agent may be an aqueous alkali solution, or an alkali-containing solid material (for example, soda lime or the like) . The preferred treatment agents are water and aqueous alkali solutions. The preferred aqueous alkali solutions are sodium hydroxide and potassium hydroxide, with the aqueous alkali solution concentration being in the range of 0.01-20% and especially in the range of 0.1-10%. The contact time is not particularly restricted but the contact temperature is preferably in a lower temperature range because of the rather high solubility of HFC-41 in water, and specifically the range is preferably 5-4O0C.
The HCl concentration of the HFC-41 subjected to acid component removal treatment is 1.0 ppm by mass or lower (measurement by ion chromatography) .
As moisture is present in the acid component-removed HFC-41, it is preferably contacted with zeolite for moisture removal. The zeolite is preferably zeolite with a small pore size such as Molecular Sieve 3A and/or Molecular Sieve 4A, considering the small molecular size of HFC-41 and the heat generation and decomposition due to heat of adsorption, and moisture removal-treated HFC- 41 results in a moisture concentration of 10 ppm by mass or less (measuring apparatus: Carl Fisher) . The present invention will now be explained in greater detail by examples, with the understanding that the invention is not limited only to these examples. Example 1 Catalyst Preparation Example 1 A solution of 452 g of Cr (NO3) 3- 9H2O and 42 g of
In (NO3) 3-nH2O (n = approximately 5) in 1.2 L of purified water and 0.3 L of 28% aqueous ammonia were added dropwise into a 10 L vessel containing 0.6 L of purified water while stirring for a period of about 1 hour, while controlling the flow rate of the two aqueous solutions so that the reaction solution pH was in the range of 7.5- 8.5. The obtained hydroxide slurry was filtered and thoroughly washed with purified water, and then dried at 1200C for 12 hours. The obtained solid was pulverized and then mixed with graphite and formed into pellets using a tableting machine. The pellets were fired at 4000C for 4 hours under a nitrogen stream to obtain a catalyst precursor. The catalyst precursor was packed into an inconel reactor, and then subjected to fluorination treatment (catalyst activation) at 3500C at ordinary pressure, under a nitrogen-diluted hydrogen fluoride stream and then under a 100% hydrogen fluoride stream, to prepare a catalyst. Example 2
Catalyst Preparation Example 2 As a catalyst carrier there was used active alumina (NST-7, by Nikki Universal Co., Ltd.) produced having a center pore size of 50-400 A, consisting of at least 70% pores with a distribution of ±50% of the center size and having a pore volume in the range of 0.5-1.6 ml/g, and having a purity of 99.9 mass% or greater and a sodium content of no greater than 100 ppm. '
After loading 191.5 g of chromium chloride (CrCl3- 6H2O) in 132 ml of purified water, the mixture was heated to 70-800C in a hot water bath for dissolution. The solution was cooled to room temperature, and then 400 g of the aforementioned active alumina was immersed therein until total absorption of the solution into the alumina. Next, the wetted alumina was dried to hardness over a 9O0C hot water bath. The hardened catalyst was dried for 3 hours in an air-circulating hot-air drier. The catalyst was then packed into an inconel reactor and subjected to fluorination treatment (catalyst activation) at 3300C at ordinary pressure, under a nitrogen-diluted hydrogen fluoride stream and then under a 100% hydrogen fluoride stream, to prepare a catalyst.
Example 3
Catalyst Preparation Example 3 A catalyst was obtained in the same manner as
Catalyst Preparation Example 2, except that 16.57 g of zinc chloride (ZnCl2) was added as a second component to the Catalyst Preparation Example 2 of Example 2.
Example 4 Commercially available methyl chloride (99.9 vol% purity, moisture content: 48 ppm by mass) was contacted with zeolite (Molecular Sieve 3A (Union Showa Co., Ltd., mean pore size: 3 A)) in a liquid phase before being supplied to the reaction system, and the moisture in the methyl chloride was analyzed with a moisture meter (Carl Fisher) to be 6 ppm by mass.
After packing 80 ml of the catalyst prepared in Catalyst Preparation Example 1 in Example 1 in an Inconel 600 reactor with an inner diameter of 1 inch and a length of 1 m, the temperature was kept at 3000C and the pressure at 0.25 MPa while circulating nitrogen gas, after which hydrogen fluoride was supplied at 73.85 NL/hr, the supply of nitrogen gas was terminated and then the aforementioned zeolite-treated methyl chloride was supplied at 6.15 NL/hr to initiate the reaction. After approximately 3 hours, the acid component of the reactor outlet gas was removed with an aqueous alkali solution and analyzed by gas chromatography. The results were as follows. CH3F 18.9470 CH3Cl 80.9100
Other 0.1431 (units: vol%)
The methyl chloride conversion rate was approximately 19.1%, and the fluoromethane selectivity was approximately 99.2%. Example 5
Reaction and analysis were conducted under the same conditions and by the same procedure as Example 4, except that 80 ml of the catalyst prepared in Catalyst Preparation Example 2 of Example 2 was packed. The results were as follows.
CH3F 19.7816 CH3Cl 80.0976 Other 0.1208 (units: vol%)
Satisfactory results were obtained, with a fluoromethane selectivity of approximately 99.4%.
Next, purified water was added to the aforementioned commercially available methyl chloride (moisture content: 48 ppm by mass) , to prepare a methyl chloride starting material having a moisture concentration of 208 ppm by mass in the methyl chloride. The supply of the zeolite- treated methyl chloride was terminated, and the methyl chloride with a moisture concentration of 208 ppm by mass was supplied to reinitiate the reaction. After approximately 8 hours, the acid component of the reactor outlet gas was removed with an aqueous alkali solution and analyzed by gas chromatography. The results were as follows. CH3F 17.4412 CH3Cl 82.1959
Other 0.3629 (units: vol%)
As seen from these results, moisture in the methyl chloride starting material is undesirable because it adversely affects the reaction, reducing the conversion rate and selectivity.
Example 6
Reaction and analysis were conducted under the same conditions and by the same procedure as Example 4, except that 80 ml of the catalyst prepared in Catalyst Preparation Example 3 of Example 3 was packed, and the reaction temperature was 250°C. The results were as follows.
CH3F 15.2266 CH3Cl 84.7576
Other 0.0158 (units: vol%) Satisfactory results were obtained, with a fluoromethane selectivity of approximately 99.9%.
Next, the reactor outlet gas was recovered in a vessel equipped with a cooler, and the recovered mixture was subjected to distillation. The recovered mixture was first introduced into a distillation column. The distillation column was provided with a condenser and had 20 theoretical plates (36 actual plates) ; the low- boiling-point components HCl and CH3F separated at the top of the column while the high-boiling-point components CH3CI and HF separated at the bottom of the column. The HCl and CH3F separated from the top were contacted with a 2% aqueous potassium hydroxide solution at a temperature of about 5°C, and then the HCl concentration of the HFC- 41 was analyzed by ion chromatography, yielding a HCl concentration of 0.5 ppm by mass.
After being contacted with the aforementioned aqueous alkali solution, the HFC-41 was contacted with zeolite (Molecular Sieve 3A (Union Showa Co., Ltd.)) and the moisture content of the HFC-41 was analyzed with a moisture meter (Carl Fisher) for a moisture concentration of 4 ppm by mass, demonstrating that high purity HFC-41 had been obtained.
Industrial Applicability
The present invention allows efficient separation of HCl from mixtures containing HFC-41 and HCl to obtain high purity HFC-41, and is therefore of high industrial utility.

Claims

1. A process for producing fluoromethane comprising the following four steps:
(1) a step of contacting methyl chloride with zeolite in a liquid phase,
(2) a step of reacting the methyl chloride obtained in step (1) with hydrogen fluoride in a gas phase in the presence of a fluorination catalyst to obtain, predominantly, fluoromethane, (3) a step of feeding the fluoromethane- containing mixed gas obtained in step (2) to a distillation column, and separating the overhead fraction comprising, predominantly, fluoromethane and hydrogen chloride from the bottom fraction comprising predominantly methyl chloride and hydrogen fluoride, and
(4) a step of separating and purifying the fluoromethane from the overhead fraction obtained in step (3) .
2. A fluoromethane production process according to claim 1, which further comprises a step of circulating the bottom fraction obtained in step (3) to step (2) .
3. A fluoromethane production process according to claim 1 or 2, wherein the zeolite used in step (1) is Molecular Sieve 3A and/or Molecular Sieve 4A.
4. A fluoromethane production process according to claim 1, wherein the fluorination catalyst used in step (2) is a supported catalyst or bulk catalyst composed mainly of trivalent chromium oxide and containing at least one element selected from the group consisting of In, Zn, Ni, Co, Mg and Al.
5. A fluoromethane production process according to claim 1 or 4, wherein the fluorination catalyst used in step (2) is a supported catalyst supported on active alumina, wherein the active alumina is produced having a center pore size of 50-400 A, consisting of at least 70% pores with a distribution of ±50% of the center size and having a pore volume in the range of 0.5-1.6 ml/g, and has a purity of 99.9 mass% or greater and a sodium content of no greater than 100 ppm.
6. A fluororaethane production process according to claim 1, 4 or 5, wherein the reaction temperature in step 2 is 150-350°C.
7. A fluoromethane production process according to claim 1, wherein the distillation in step (3) is carried out in a pressure range of 0.1-5 MPa.
8. A fluoromethane production process according to claim 1, wherein the separation and purification step in step (4) further comprises a step of contacting the fluoromethane with water and/or an alkali-containing treatment agent to remove the acid component containing hydrogen chloride.
9. A fluoromethane production process according to claim 8, which further comprises a step of contacting the fluoromethane with zeolite after the step of removing the acid component in said fluoromethane.
10. A fluoromethane production process according to claim 9, wherein said zeolite is Molecular Sieve 3A and/or Molecular Sieve 4A.
11. A fluoromethane product containing fluoromethane which is obtained by the process according to any one of claims 1 to 10 and has a hydrogen chloride concentration of no greater than 1.0 ppm by mass.
12. A fluoromethane product containing fluoromethane which is obtained by the process according to any one of claims 1 to 10 and has a moisture concentration of no greater than 10 ppm by mass.
PCT/JP2005/016474 2004-09-16 2005-09-01 Fluoromethane production process and product WO2006030677A1 (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110184209A1 (en) * 2008-10-06 2011-07-28 Showa Denko K.K. Process for producing carbonyl difluoride
CN113816826A (en) * 2021-11-03 2021-12-21 中船重工（邯郸）派瑞特种气体有限公司 Purification method of electronic-grade monofluoromethane

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JPS608235A (en) * 1983-06-28 1985-01-17 Showa Denko Kk Production of fluoromethane
JPS608234A (en) * 1983-06-27 1985-01-17 Showa Denko Kk Production of fluoromethane
JPS6013726A (en) * 1983-07-04 1985-01-24 Showa Denko Kk Preparation of fluoromethane

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JPS608234A (en) * 1983-06-27 1985-01-17 Showa Denko Kk Production of fluoromethane
JPS608235A (en) * 1983-06-28 1985-01-17 Showa Denko Kk Production of fluoromethane
JPS6013726A (en) * 1983-07-04 1985-01-24 Showa Denko Kk Preparation of fluoromethane

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110184209A1 (en) * 2008-10-06 2011-07-28 Showa Denko K.K. Process for producing carbonyl difluoride
US8664438B2 (en) * 2008-10-06 2014-03-04 Showa Denko K.K. Process for producing carbonyl difluoride
TWI461362B (en) * 2008-10-06 2014-11-21 Showa Denko Kk Production method of difluorinated carbonyl group
CN113816826A (en) * 2021-11-03 2021-12-21 中船重工（邯郸）派瑞特种气体有限公司 Purification method of electronic-grade monofluoromethane
CN113816826B (en) * 2021-11-03 2023-05-02 中船(邯郸)派瑞特种气体股份有限公司 Purification method of electronic grade monofluoromethane

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